1. Field of the Invention
The present invention relates generally to non-oriented electrical steel sheet, having excellent texture characteristics for use in motors, generators, small sized transformers and the like, and a method for manufacturing the same.
2. Description of Related Art
Soft magnetic steel sheets require two major magnetic properties such as a low core loss and a high magnetic flux density. The methods of reducing the iron loss of the soft magnetic steel sheets include facilitating the movements of magnetic domains (reducing hysteresis loss), and increasing the resistivity (reducing eddy current loss).
In order to facilitate the movement of the magnetic domains, impurities such as oxygen, carbon, nitrogen, and titanium should be removed to improve the purity of the iron or iron-base alloys. In order to increase the resistivity, contents of silicon, aluminum and manganese should be increased.
Since Fe-base bcc (body-centered cubic) crystals are magnetically anisotropic, crystallographic texture is known to affect magnetic properties of iron or iron-base alloy sheets significantly. The optimum texture of non-oriented electrical steel sheets is {100} plane parallel to the sheet surface (hereafter referred as {100} texture) because the {100} plane has two easy magnetization directions, <001>, and no hard magnetization direction, <111>.
There are known methods for manufacturing {100} texture. When a thin Fe-3% Si was annealed in H2S atmosphere at not less than 1000° C., preferential growth of grains with {100} planes parallel to the surface of the sheet was observed. Sulfur or oxygen is considered to adsorb on the surface and cause the anisotropy of the surface energy at the annealing atmosphere. In the direct casting method which the present inventor disclosed in Korean Patent Application Laid-open No. 95-48472/1995, a high density {100} texture is observed in silicon steel sheet. However, since the silicon steel sheet has a rough surface and irregular thickness, the problems should be resolved to use the silicon steel sheet as electrical steels.
As mentioned above, there are known methods for manufacturing a soft magnetic steel sheets with {100} texture. However, since these processes have problems for mass production, it is not easy to manufacture the soft magnetic steel sheet with {100} texture commercially.